The present development relates to a fluid/slurry bed catalyst prepared by compounding cobalt with alumina, followed by spray drying. The resultant catalyst is easier to prepare than catalysts of the prior art because it is made using a one-pot compounding method. Further, the catalyst of the present invention has a more uniform cobalt loading, and can have a higher cobalt loading than catalysts of the prior art. The resulting catalyst surprisingly also has low attrition, a desirable cobalt crystallite size, and is fully reducible.
Cobalt on alumina catalysts are often used in chemical processes such as Fischer-Tropsch reactions, unsaturated hydrocarbon hydrogenation or alcohol amination reactions, and methods for preparing cobalt on alumina catalysts are known in the art. The most common method for preparation involves impregnating an alumina support with a cobalt-containing solution, then drying and calcining the cobalt-impregnated support, and repeating the procedure until the desired cobalt level is achieved. However, this is a time-consuming and labor-intensive process. For example, to produce a catalyst with about a 20 wt % cobalt loading typically requires up to nine steps including three separated dipping steps, three drying steps and three calcinations steps.
An alternative method of preparing a cobalt on alumina catalyst is disclosed in U.S. Pat. No. 4,179,411 (issued to Broersma et al. on Dec. 18, 1979, and assigned to Nalco Chemical Company). The '411 patent claims a method comprising preparing an alumina hydroxide gel, then purifying, forming, drying and calcining the gel. The resultant catalyst has a controlled pore volume distribution. The alumina hydroxide gel is prepared by precipitating an aluminum hydroxide from a solution of soluble aluminum salts. The precipitation is achieved by titrating the soluble aluminum salt solution with an acid or basic solution to bring the resulting pH into the range from 5-9 where a white aluminum hydroxide precipitate appears. A requirement of the claimed invention is that a polycarboxylic acid, having from 2-12 carbon atoms such as the preferred citric acid and oxalic acids, is dissolved in either the aluminum salt solution or in the titrating solution.
U.S. Pat. No. 6,353,035 (issued to Manzer et al. on Mar. 5, 2002 and assigned to Conoco, Inc.) claims a process for producing hydrocarbons from hydrogen and carbon monoxide. The catalyst is prepared by a method comprising (1) forming a catalyst gel by destabilizing the aqueous colloid comprising (a) at least one catalytic metal for Fischer-Tropsch reactions, (b) at least one colloidal oxide selected from the group consisting of cerium oxide, zirconium oxide, titanium oxide and aluminum oxide, and optionally (c) at least one alkoxide selected from the group consisting of Al(OR)3, Si(OR)4, Ti(OR)5 and Zr(OR)4, where each R is an alkyl group having from 1 to 6 carbon atoms; and (2) drying the gel. The catalytic metals recommended include iron, cobalt, nickel, ruthenium and combinations thereof. The challenge presented for the '035 catalyst preparation lies in drying the gel. In the examples recited, the gels are aged for several days and then dried under vacuum. Alternatively, a water solvent can be exchanged with a non-aqueous solvent before the gel is subjected to supercritical pressure extraction. While these drying methods are effective in the laboratory, they can be difficult and expensive to use in commercial production of a bulk catalyst.